Risk factors for malaria: a microepidemiological study in a village in Sri Lanka.

Environmental and socioeconomic risk factors for malaria were studied in a village in Sri Lanka. Over a period of one year, all 49 households in the village were visited every alternate day to obtain information on malaria episodes. Information on risk factors was obtained through questionnaires and direct observations. Age below 17 years (relative risk [RR] = 1.66, 95% confidence interval [95% CI] 1.18-2.35), use of bed nets (RR = 0.16, 95% CI 0.05-0.45) and traditional fumigants (RR = 0.58, 95% CI 0.37-0.93) were independent predictors of malaria. People using anti-mosquito pyrethrum coils had a higher risk for malaria than people living in houses where they were not used (RR = 1.46, 95% CI 1.03-2.07). The build-up of Anopheles culicifacies populations before the start of the transmission season had taken place in a stream near the village. Living close to the stream was a risk factor for malaria early in the transmission season, although this did not reach statistical significance (comparing < 250 m with > 500 m, RR = 2.13, 95% CI 0.96-4.71).